At present, a user of a set-top box (STB) or an internet protocol television (IPTV) without a standard keyboard may operate a virtual keyboard with a remote control device to input characters. The user should press directional control buttons of the remote control device to select keys corresponding to the characters. However, the present virtual keyboard is quadrate. If the keys corresponding to the characters are far away from each other, the remote control device buttons must be pressed many times. For example, if the user wants to input a word “WORLD”, he/she should press the remote control device 29 times.